The growth in the use, and usefulness, of semiconductors has been accompanied by the development of new processes and materials for the design and manufacture of semiconductors together with new or improved manufacturing equipment and hardware. Important recent improvements in design and new materials have led to faster speeds of operation and greater densities for very large scale integrated (VLSI) circuits. The use of new materials such as tantalum, titanium, and other metals, has led to the need for more efficient ways of applying them to semiconductor surfaces.
A layer or film of a metal such as tantalum, titanium, etc. can be deposited by chemical vapor deposition (CVD) onto exposed surfaces of a semiconductor wafer during processing into VLSIs. For example, a precursor compound of the metal tantalum, namely pentadiethylaminotantalum (PDEAT), can be vaporized under certain conditions of pressure and temperature to obtain a gaseous or vapor phase of the compound which may then be used in CVD processing to form a layer of metal. Precursor compounds of various metals require low pressures (e.g., a Torr or less and elevated temperatures (e.g., roughly 100.degree. C.) to change them into and hold them in vapor phase. This will be explained in greater detail hereinafter.
It is desirable that a layer of metal being deposited by CVD on a semiconductor wafer be uniform in thickness. To achieve this, a chemical vapor precursor compound of the metal flowing into a processing chamber where the semiconductor wafer is being processed should be controlled in flow direction and amplitude so that the vapor is evenly distributed and flows uniformly toward the wafer. In addition, because a CVD process step using a precursor compound of a metal such as tantalum, titanium, etc., is typically carried out in a chamber maintained under low pressure conditions (e.g., a Torr or less), the flow of gas vapor into the chamber through a vaporizer head should be impeded as little as possible by the head. The head should have high-flow-conductance so that pressure drop across it is low (e.g., a fraction of a Torr). The gas vapor should also be controlled in temperature as it passes through the head and enters the chamber to prevent condensation of the vapor into droplets or particles.
The present invention provides a simple and efficient vaporizer head with improved characteristics which fills these needs.